The present invention relates to a high-frequency power amplifier. More particularly, the invention relates to a technology effectively applicable to a high-frequency power amplifier that has multiple power modes and switches transistors used for the modes.
For example, patent document 1 describes the RF (Radio Frequency) amplifier that includes the high-power signal path, the low-power signal path, and the bypass signal path. Patent document 2 describes the high-frequency power amplifier that includes three paths between an input terminal and an output terminal and provides each path with a transistor and an output matching circuit. The transistors for the paths are differently sized. Patent document 3 describes the high-frequency power amplification module including the small output amplification portion and the large output amplification portion whose outputs are coupled to the common output matching circuit. The input matching circuit having high isolation characteristics is provided as an input portion for the small output amplification portion and the large output amplification portion.
Patent document 4 describes the high-frequency power amplifier that includes two paths between the input-side branch circuit and the output-side branch circuit. The variable phase shifter is provided near the input-side branch circuit. Patent document 5 describes the high-frequency power amplifier module that includes two paths between the input terminal and the output terminal and provides each path with the two-stage transistor and various matching circuits. One of the paths includes the switch circuit that short-circuits the path to the ground voltage.    Patent document 1: US patent No. 2009/0309656    Patent document 2: Japanese Unexamined Patent Publication No. 2002-271146    Patent document 3: Japanese Unexamined Patent Publication No. 2006-93773    Patent document 4: Japanese Unexamined Patent Publication No. 2003-87060    Patent document 5: Japanese Unexamined Patent Publication No. 2003-87059